使用kotlin集成springboot开发的超详细教程

目前大多数都在使用java集成 springboot进行开发，本文演示仅仅将 java换成 kotlin，其他不变的情况下进行开发。

一、安装支持插件

在 idea中安装 kotlin插件（大多数情况下会默认安装了）

二、maven配置 注意

kotlin目前不支持 lombok所以不能使用或引用 lombok相关的插件或依赖包，下面是一个排除示例，同时也不支持 maven-enforcer-plugin

<dependency>
          <groupId>com.ayouran.common</groupId>
          <artifactId>a-common</artifactId>
          <version>1.0.0-SNAPSHOT</version>
          <exclusions>
               <exclusion>
                     <groupId>org.projectlombok</groupId>
                     <artifactId>lombok</artifactId>
               </exclusion>
          </exclusions>
</dependency>

maven的属性配置

<properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
      <maven.compiler.source>1.8</maven.compiler.source>
      <maven.compiler.target>1.8</maven.compiler.target>
      <kotlin.version>1.3.21</kotlin.version>
      <!--增量编译-->
      <kotlin.compiler.incremental>true</kotlin.compiler.incremental>
      <!--关闭协程编译警告-->
      <experimentalCoroutines>enable</experimentalCoroutines>
      <spring-boot.version>2.2.4.RELEASE</spring-boot.version>
      <spring-cloud.version>Hoxton.SR1</spring-cloud.version>
      <swagger.version>2.7.0</swagger.version>
      <main.class>com.lc.github.KotlinDemoApplication</main.class>
      <querydsl.version>4.2.1</querydsl.version>
      <mapstruct.version>1.3.1.Final</mapstruct.version>
  </properties>

必要的依赖

<dependencies>
     <!--反射支持包，不需要可以去掉-->
      <dependency>
          <groupId>org.jetbrains.kotlin</groupId>
          <artifactId>kotlin-reflect</artifactId>
          <version>${kotlin.version}</version>
      </dependency>
   <!--jdk8下的 kotlin支持包-->
      <dependency>
          <groupId>org.jetbrains.kotlin</groupId>
          <artifactId>kotlin-stdlib-jdk8</artifactId>
          <version>${kotlin.version}</version>
      </dependency>
  </dependencies>

编译部分

<build>
      <plugins>
          <plugin>
              <groupId>org.jetbrains.kotlin</groupId>
              <artifactId>kotlin-maven-plugin</artifactId>
              <configuration>
                  <correctErrorTypes>true</correctErrorTypes>
                  <languageVersion>${kotlin.language.version}</languageVersion>
              </configuration>
              <dependencies>
                  <dependency>
                      <groupId>org.jetbrains.kotlin</groupId>
                      <artifactId>kotlin-maven-allopen</artifactId>
                      <version>${kotlin.version}</version>
                  </dependency>
              </dependencies>
              <executions>
                  <execution>
                      <id>kapt</id>
                      <goals>
                          <goal>kapt</goal>
                      </goals>
                      <configuration>
                          <correctErrorTypes>true</correctErrorTypes>
                          <sourceDirs>
                              <sourceDir>src/main/kotlin</sourceDir>
                              <sourceDir>src/main/java</sourceDir>
                          </sourceDirs>
                          <annotationProcessorPaths>
                              <annotationProcessorPath>
                                  <groupId>com.google.dagger</groupId>
                                  <artifactId>dagger-compiler</artifactId>
                                  <version>2.9</version>
                              </annotationProcessorPath>
                              <annotationProcessorPath>
                                  <groupId>com.querydsl</groupId>
                                  <artifactId>querydsl-apt</artifactId>
                                  <version>${querydsl.version}</version>
                                  <classifier>jpa</classifier>
                              </annotationProcessorPath>
                              <annotationProcessorPath>
                                  <groupId>org.mapstruct</groupId>
                                  <artifactId>mapstruct-processor</artifactId>
                                  <version>${mapstruct.version}</version>
                              </annotationProcessorPath>
                          </annotationProcessorPaths>
                      </configuration>
                  </execution>
                  <execution>
                      <id>compile</id>
                      <goals>
                          <goal>compile</goal>
                      </goals>
                      <configuration>
                          <sourceDirs>
                              <sourceDir>src/main/kotlin</sourceDir>
                              <sourceDir>src/main/java</sourceDir>
                          </sourceDirs>
                      </configuration>
                  </execution>
                  <execution>
                      <id>test-kapt</id>
                      <goals>
                          <goal>test-kapt</goal>
                      </goals>
                      <configuration>
                          <sourceDirs>
                              <sourceDir>src/test/kotlin</sourceDir>
                              <sourceDir>src/test/java</sourceDir>
                          </sourceDirs>
                          <annotationProcessorPaths>
                              <annotationProcessorPath>
                                  <groupId>com.google.dagger</groupId>
                                  <artifactId>dagger-compiler</artifactId>
                                  <version>2.9</version>
                              </annotationProcessorPath>
                              <annotationProcessorPath>
                                  <groupId>com.querydsl</groupId>
                                  <artifactId>querydsl-apt</artifactId>
                                  <version>${querydsl.version}</version>
                                  <classifier>jpa</classifier>
                              </annotationProcessorPath>
                              <annotationProcessorPath>
                                  <groupId>org.mapstruct</groupId>
                                  <artifactId>mapstruct-processor</artifactId>
                                  <version>${mapstruct.version}</version>
                              </annotationProcessorPath>
                          </annotationProcessorPaths>
                      </configuration>
                  </execution>
                  <execution>
                      <id>test-compile</id>
                      <goals>
                          <goal>test-compile</goal>
                      </goals>
                      <configuration>
                          <sourceDirs>
                              <sourceDir>src/test/kotlin</sourceDir>
                              <sourceDir>src/test/java</sourceDir>
                              <sourceDir>target/generated-sources/kapt/test</sourceDir>
                          </sourceDirs>
                      </configuration>
                  </execution>
              </executions>
          </plugin>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-compiler-plugin</artifactId>
              <version>3.8.1</version>
              <configuration>
                  <proc>none</proc>
                  <source>${java.version}</source>
                  <target>${java.version}</target>
                  <annotationProcessorPaths>
                      <path>
                          <groupId>org.projectlombok</groupId>
                          <artifactId>lombok</artifactId>
                          <version>${lombok.version}</version>
                      </path>
                      <path>
                          <groupId>org.mapstruct</groupId>
                          <artifactId>mapstruct-processor</artifactId>
                          <version>${mapstruct.version}</version>
                      </path>
                  </annotationProcessorPaths>
                  <compilerArgs>
                      <arg>-Amapstruct.suppressGeneratorTimestamp=true</arg>
                      <arg>-Amapstruct.defaultComponentModel=spring</arg>
                  </compilerArgs>
              </configuration>
              <executions>
                  <!-- Replacing default-compile as it is treated specially by maven -->
                  <execution>
                      <id>default-compile</id>
                      <phase>none</phase>
                  </execution>
                  <!-- Replacing default-testCompile as it is treated specially by maven -->
                  <execution>
                      <id>default-testCompile</id>
                      <phase>none</phase>
                  </execution>
                  <execution>
                      <id>java-compile</id>
                      <phase>compile</phase>
                      <goals>
                          <goal>compile</goal>
                      </goals>
                  </execution>
                  <execution>
                      <id>java-test-compile</id>
                      <phase>test-compile</phase>
                      <goals>
                          <goal>testCompile</goal>
                      </goals>
                  </execution>
              </executions>
          </plugin>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-assembly-plugin</artifactId>
              <version>2.6</version>
              <executions>
                  <execution>
                      <id>make-assembly</id>
                      <phase>package</phase>
                      <goals>
                          <goal>single</goal>
                      </goals>
                      <configuration>
                          <archive>
                              <manifest>
                                  <mainClass>${main.class}</mainClass>
                              </manifest>
                          </archive>
                          <descriptorRefs>
                              <descriptorRef>jar-with-dependencies</descriptorRef>
                          </descriptorRefs>
                      </configuration>
                  </execution>
              </executions>
          </plugin>
      </plugins>
  </build>

有 java与 kotlin混合的情况，在上面的 <plugins>下加入下面的编译插件

<plugin>
                          <groupId>org.apache.maven.plugins</groupId>
                          <artifactId>maven-compiler-plugin</artifactId>
                          <version>3.8.1</version>
                          <configuration>
                              <proc>none</proc>
                              <source>${java.version}</source>
                              <target>${java.version}</target>
                              <annotationProcessorPaths>
                                  <path>
                                      <groupId>org.mapstruct</groupId>
                                      <artifactId>mapstruct-processor</artifactId>
                                      <version>${mapstruct.version}</version>
                                  </path>
                              </annotationProcessorPaths>
                              <compilerArgs>
                                  <arg>-Amapstruct.suppressGeneratorTimestamp=true</arg>
                                  <arg>-Amapstruct.defaultComponentModel=spring</arg>
                              </compilerArgs>
                          </configuration>
                          <executions>
                              <!-- Replacing default-compile as it is treated specially by maven -->
                              <execution>
                                  <id>default-compile</id>
                                  <phase>none</phase>
                              </execution>
                              <!-- Replacing default-testCompile as it is treated specially by maven -->
                              <execution>
                                  <id>default-testCompile</id>
                                  <phase>none</phase>
                              </execution>
                              <execution>
                                  <id>java-compile</id>
                                  <phase>compile</phase>
                                  <goals>
                                      <goal>compile</goal>
                                  </goals>
                              </execution>
                              <execution>
                                  <id>java-test-compile</id>
                                  <phase>test-compile</phase>
                                  <goals>
                                      <goal>testCompile</goal>
                                  </goals>
                              </execution>
                          </executions>
                      </plugin>

此 maven配置集成了 querydsl、mapstruct、dagger2的编译，基本上能满足常规的使用

三、创建入口函数类

四、编写入口函数

springboot的启动方法及 swagger的配置

@EnableAsync
@EnableSwagger2
@EnableScheduling
@SpringBootApplication
class KotlinDemoApplication : CommandLineRunner {
  companion object {
      @JvmStatic
      fun main(args: Array<String>) {
          SpringApplication.run(KotlinDemoApplication::class.java, *args)
      }
  }

  @Bean
  fun api(): Docket {
      return Docket(DocumentationType.SWAGGER_2)
              .ignoredParameterTypes(Session::class.java)
              .select()
//                .apis(RequestHandlerSelectors.any())
              .apis(RequestHandlerSelectors.basePackage("com.ayouran.flow.controllers"))
              .paths(PathSelectors.any())
              .build()
              .apiInfo(ApiInfoBuilder()
                      .description("ayouram-flow相关API")
                      .title("ayouram-flow")
                      .version("1.0")
                      .build())
              .pathMapping("/")
  }

  override fun run(vararg args: String?) {
      println("*************************** ok ***********************************")
  }
}

五、创建数据库对象

import com.fasterxml.jackson.annotation.JsonFormat
import org.hibernate.annotations.DynamicInsert
import org.hibernate.annotations.DynamicUpdate
import java.util.*
import javax.persistence.*

/****
* 设备流量规则
*/
@Entity
@Table(name = "device_rules",
      indexes = [Index(name = "device_no", columnList = "device_no"),
          Index(name = "rules_no", columnList = "rules_no"),
          Index(name = "deleted", columnList = "deleted")],
      uniqueConstraints = [UniqueConstraint(name = "device_no_rules_no", columnNames = ["device_no", "rules_no"])])
@DynamicUpdate
@DynamicInsert
class DeviceRules {

  @Id
  @Column(name = "id", columnDefinition = "bigint(20) COMMENT 'ID,自增'")
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  var id: Long? = null

  @Column(name = "device_no", columnDefinition = "varchar(18) COMMENT '设备编号'")
  var deviceNo: String? = null

  @Column(name = "rules_no", columnDefinition = "varchar(18) COMMENT '规则编号'")
  var rulesNo: String? = null

  @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")
  @Column(name = "create_at", columnDefinition = "datetime COMMENT '创建时间'")
  var createAt: Date? = null

  @Column(name = "update_at", columnDefinition = "datetime COMMENT '修改时间'")
  var updateAt: Date? = null

  /**
   * 触发jpa update代码需要执行的逻辑
   */
  @PreUpdate
  fun preUpdate() {
      updateAt = Date()
  }

  /**
   * 自动设置必要字段的值
   */
  @PrePersist
  fun prePersist() {
      updateAt = Date()
      createAt = updateAt
      deleted = BaseEnum.NOT_REMOVE.index
  }
}

注解使用了 hibernate的功能主要用于自动创建/更新表结构以及索引的生成，如果需要 mybatis版本的，只需要去掉这里面的注释就好。

六、创建仓库操作接口

基于 springboot-data-jpa的 repository

@Repository
interface DeviceRulesRepository : JpaRepository<DeviceRules, Long>,
      JpaSpecificationExecutor<DeviceRules>, QuerydslPredicateExecutor<DeviceRules> {
  fun getAllByDeviceNoAndDeleted(deviceNo: String, deleted: Int): Optional<MutableList<DeviceRules>>
}

七、创建一个业务接口来声明业务

interface DeviceService {

  /**
   * 查询设备的路由规则
   */
  fun queryDeviceFlowRules(aPageRequest: APageRequest): PageResult<QueryDeviceFlowRulesVO>
}

八、创建一个业务接口实现来实现声明的业务

@Service
class DeviceServiceImpl @Autowired
constructor(private val deviceRepository: DeviceRepository,
          private val deviceRulesRepository: DeviceRulesRepository,
          private val querydslUtlis: QuerydslUtlis,
          private val deviceMapstruct: DeviceMapstruct) : DeviceService {
  private val logger = LoggerFactory.getLogger(javaClass)
  
  override fun queryDeviceFlowRules(aPageRequest: APageRequest): PageResult<QueryDeviceFlowRulesVO> {
      val qDeviceRules = QDeviceRules.deviceRules
      val qFlowRules = QFlowRules.flowRules
      var rredicate: Predicate? = null
      if (StringUtils.isNotBlank(aPageRequest.query)) rredicate = qDeviceRules.deviceNo.eq(aPageRequest.query)
      val exprs = arrayOf<Expression<*>>(qDeviceRules.deviceNo, qDeviceRules.deleted, qFlowRules.rulesNo, qFlowRules.flowMax,
              qFlowRules.startTime, qFlowRules.endTime)
      val results = querydslUtlis.getQueryFactory()
              .select(*exprs)
              .from(qDeviceRules)
              .where(ExpressionUtils.allOf(rredicate))
              .leftJoin(qFlowRules)
              .on(qDeviceRules.rulesNo.eq(qFlowRules.rulesNo))
              .orderBy(qDeviceRules.createAt.desc())
              .offset((aPageRequest.pageIndex!! - 1) * aPageRequest.pageSize!!)
              .limit(aPageRequest.pageSize!!)
              .fetchResults()
      return PageUtlis.retPage(results, querydslUtlis.getCollection(results.results, exprs, QueryDeviceFlowRulesVO::class.java) as Collection<QueryDeviceFlowRulesVO>)
  }
}

这里使用了 querydsl来完成一个多表查询

九、创建一个 http服务接口

@RestWrapper
@RestController
@RequestMapping("/device")
@Api(value = "device", description = "设备相关接口", tags = ["device"])
class DeviceController @Autowired
constructor(private val deviceService: DeviceService) {

  @GetMapping("/query_device")
  fun queryDevice(aPageRequest: APageRequest) = deviceService.queryDevice(aPageRequest)

  @GetMapping("/query_device_flow_rules")
  fun queryDeviceFlowRules(aPageRequest: APageRequest) = deviceService.queryDeviceFlowRules(aPageRequest)
}

至此完成一个基本的开发过程，大多数情况下可以直接将 java代码粘贴到 kotlin文件中，会自动转换成合适的 kotlin代码(偶尔需要自己调整，毕竟编辑器不是万能的)

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原文链接：https://blog.csdn.net/u012599432/article/details/105455503